A well-washed negative will keep better over time
This question is important for the preservation of negatives. Indeed, a negative that appears clean may not be entirely so.
Residues of fixer may remain on the surface, which will degrade the negative in the months or years to come.
Similarly, over-washing your negatives can harm their long-term preservation [1].
So, how should you wash your negatives properly?
How can you tell if a negative is clean?
You can read all sorts of things on the internet about the supposed effectiveness of washing methods.
However, there is nothing esoteric about it: there are ways of measuring the amount of fixer residue on the negative after washing. And these are the ones that count.
The Ilford washing method below removes fixer residue [2]. It takes no more than 3 minutes and uses a minimum amount of water.
The method recommended by Ilford [3] (and which I use)
- Fill the tank with water. Close the tank. Turn the tank over 5 times. Empty the tank.
- Fill the tank with water. Close the tank. Turn the tank over 10 times. Empty the tank.
- Fill the tank with water. Close the tank. Perform 15 turns. Empty the tank.
- Rinse by filling the tank with water (I use distilled water for this step) while adding wetting agent in the correct proportions (1+200 for ilfotol).
One small subtlety, however
The above method works with fixers that are not tanning/hardening (which is usually the case, as for Ilford hypo and rapid fixers). For fixers that are tanning/hardening, the washing time must be extended.
[1] “Over-washing can actually reduce the archival properties of film, as thiosulfate in very small concentrations has been shown to have a beneficial effect on film image stability.[3]” (https://en.wikipedia.org/wiki/Washing_(photography)).
[2] “The tests showed no detectable residual hypo” https://merefilmphoto.com/2019/10/12/washing-film-the-ilford-method/
[3] https://www.ilfordphoto.com/wp/wp-content/uploads/2017/03/Reducing-Wash-Water.pdf
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